This invention relates to an improvement in an oil control piston ring assembly of the type having an expander and side rails.
An oil control piston ring assembly, which is used in combination with a pressure ring, is fitted into the groove of a piston employed primarily in internal combustion engines. The piston ring assembly includes a pair of annular side rails the outer peripheral edges of which contact the inner wall of the cylinder in which the piston reciprocates. The side rails thus serve to prevent leakage of oil and, hence, contribute to a reduction in oil consumption.
A problem encountered in reciprocating pistons is that the piston is prone to reciprocate within the cylinder while wobbling from side to side, rather than traveling along a fixed axis at all times. Such wobbling motion causes a variation in the contacting pressure between the cylinder wall and the side rails, one of which is located above the other, and can even cause a gap to form between the cylinder wall and the side rails. Though the reasons for such phenomena will be set forth later in a more detailed description of the prior art, it is obvious that the result will be severe leakage of oil from between the side rails and cylinder wall.